Electric shunt device



Oct. 3, i987 SHIH-WOQ ou 3,345,482

ELECTRIC SHUNT DEVICE Filed June 29. 1964 5 Sheets-Shet 1 Oct. 3, 1967 SHlH-WOO LOU 3,345,482

ELECTRIC SHUNT DEVICE Filed June 29, 1964 3 Sheets-Sheet 2 Oct. 3, 1967 Filed June 29, 1964 v SHlH-WOO LOU ELECTRIC SHUNT DEVICE S Sheets-Sheet 5 United States Patent ,0

3,345,482 ELECTRIC SHUNT DEVICE Shih-Woo Lou, 395 Queens Road 13., 4th floor, R0. Box 1076, Victoria, Hong Kong Filed June 29, 1964, Ser. No. 379,043 Claims. (Cl. 20t)118) ABSTRACT OF THE DISCLOSURE A shunt device for an electric lamp and primarily for series-connected decorative lamps, having an aluminum oxide coated aluminum plate or plates within a casing and an uncoated metal terminal plate, the plates being superimposed and being separated by electrically resistive material layers. The shunt device can be incorporated in a master control lamp or in an adaptor between a set of lamps and a supply point.

This invention concerns shunt devices and particularly, but not exclusively, safety shunt devices for use in conjunction with series connected sets of decorative electric lamps.

An inherent defect of series connected sets of decorative electric lamps is that, should one lamp fail, the remaining lamps also do not work. The useless lamp can then only be found by a process of elimination. Should two lamps fail, the combinations to be employed in the process of elimination become excessive.

To overcome this defect, it has been proposed, in the past, to use shunts in parallel with each of the lamps so that, should a particular lamp fail, its shunt automatically becomes operative and current continues to flow. However, shunts proposed heretofore have, generally, had negligible resistance so that, as a shunt came into operation so an increase in current flow occurred. This, of course, shortened the life of the remaining lamps in the set as they were then over-run. The amount-of over-running increased as more and more lamps failed until the set of lamps was passing so much current that a serious fire hazard was created, particularly if the lamps had been used in the decoration of a highly inflammable article such as a Christmas tree.

To overcome such disadvantages current limiting on constant current devices were included in the circuit. This, necessarily raised the cost of a set of lamps.

It is an object of the present invention, firstly, vide an efiicient and reliable shunt device and, secondly, to provide, in combination with such shunt device, simple and reliable current reducing means or current limiting means.

It is a further object of the present invention to provide a lamp socket incorporating the shunt device and, if desired, the current reducing means or current limiting means.

Yet another object of the present invention is to provide a master control lamp unit for use in conjunction with a set of series connected decorative lamps.

A still further object of the present invention is the provision of a series connected set of decorative electric lamps having shunt devices and current reducing means or current limiting means whereby the fire hazard heretofore presented, is obviated or reduced in an extremely convenient manner.

According to this invention the shunt device comprises a metal casing constituting one shunt terminal, an uncoated metal plate and an aluminum oxide coated plate, said plates being superimposed and spaced apart within the casing and insulated therefrom, the said uncoated metal plate constituting a second terminal with the casing havto pro- 3,345,482 Patented Oct. 3, 1967 ing an aperture for the outlet of a connecting wire therefrom, and electrically resistive material layers disposed between said plates and casing.

The invention will be described further, by way of examples, with reference to the accompanying drawings, in which:

FIGURE 1 is a section of a shunt device in accordance with the present invention;

FIGURE 2 is a view, similar to FIGURE 1 of a shunt device having current reducing means or current limiting means;

FIGURE 3 is a view similar to FIGURES l and 2, of a modification of the shunt device shown in FIGURE 2;

FIGURE 4 is a diagrammatic section of a lamp socket incorporating a simple shunt device of the kind shown in FIGURE 1 and, in series therewith, a separate resistor;

FIGURE 5 is a view, similar to FIGURE 4 of the set of series connected lamp sockets each having a shunt device in accordance with FIGURES 1, 2 or 3;

FIGURE 6 is a view similar to FIGURE 5 showing a master or control lamp and its method of employment;

FIGURE 7 is a view of an alternative form of master or control lamp, to that shown in FIGURE 6;

FIGURE?) is a circuit diagram of a control unit incorporating a flasher bulb;

FIGURE 9 is a diagrammatic section of the unit of FIGURE 8.

FIGURE 10 is a circuit diagram and FIGURE 11 illustrates an embodiment.

FIGURE 12 is a circuit diagram and FIGURE 13 is a diagrammatic illustration of an adaptor in accordance with a further embodiment of the present invention;

FIGURE 14 illustrates the manner in which a plurality of the adaptors of FIGURE 13 can be employed in parallel; and

FIGURE 15 is a diagrammatic illustration of a further embodiment of adaptor.

In the drawings, like reference numerals are employed to indicate similar parts.

As shown in FIGURE 1, a shunt device 10 constructed in accordance with the present invention comprises a substantially cylindrical metal shell 14 having a bottom 14 and bent over top portions 15. The bottom 14 constitutes a terminal and one lead of a pair leads 22 is soldered thereto.

Within the shell 14 are one or more aluminum plates 11, each coated on opposite surface with a layer 11' of aluminum oxide. Fibre insulating rings 12 each having a hollow central portion 12' are stacked one above the other in the shell. Each fibre ring 12 has a shoulder or rabetted portion 17 whereon a respective one of the aluminum plates 11 is located. The top fibre ring has an uncoated metal plate 16 located on its shoulder and this plate 16 constitutes a second terminal of the shunt device, the other lead of the pair of leads 22 being soldered thereto. The metal plate 16 and the top fibre ring 12 are spaced from the bent over top portions 15 of the shell by a fibre insulating ring 12A of internal diameter slightly less than the internal diameter of the ring 12 and the diameter or the metal plate 16. The hollow portions 12' of the fibre rings 12 are filled with an electrically conducting material, for example, metal granules 13 preferably spherical lead shot granules capable of easy movement within the hollow portions 12.

The casing bottom 14', the metal plate 16 and the aluminum plate or plates 11 may be of zig-zag, corrugated convex or concave section so as where desirable, for example, between the upper aluminum plate 11 and the metal plate 16, or between the bottom aluminum plate 11 and the casing bottom 14', or between the upper and lower aluminum plates 11 to ensure good electrical contact.

The circuit between the leads 22 is broken therefore, at the aluminum oxide layers 11'. If a suificiently high voltage is applied across the leads 22, the insulation provided by the layers 11 breaks down and the device, as a whole, becomes conducting. The breakdown voltage of aluminum oxide coated plates can be predetermined with great accuracy. Removal of the voltage from across the leads 22 and light tapping of the device is sufiicient to restore the device to its insulator state until, once again, a sufliciently high voltage is connected thereacross.

As will be described hereinafter, the metal granules may, in one or more instances, be replaced by a single piece of any electrically conducting material. Alternatively, if graphite or composition carbon granules are employed they effectively form a very desirable resistance in series with the shunt.

It is intended, as well be described hereinafter, that the shunt device be used in a lamp case of a miniature lamp of a set of decorative lamps.

It has already been mentioned that a defect, not entirely remedied by the above shunt device, is that such shunt devices permit an increase in current flow by effectively reducing the resistance of the circuit.

A modified version of the shunt device is shown in FIG- URE 2 and a further modification is shown in FIG- URE 3. Both these versions comprise essentially the parts described hereinbefore in relation to FIGURE 1 and, additionally, each includes, within the shell 14, current reducing means or current limiting means in the form of a disc-like resistor 18 surrounded by an insulating ring 19. The phrase current reducing means as used in this specification means a resistor of relatively high value, for example, equal to the resistance of a conventional set of decorative lamps. The phrase current limiting means as used in this specification means a resistor of relatively low value, for example, equal to the resistance of a single miniature lamp. Such resistor 18, which may be of the wire wound, composition carbon, deposited metal or carbon film or cracked carbon resistors, can be positioned instead of metal or other electrically conducting granules either between the bottom 14' and the lower aluminum oxide coated plate 11 (FIGURE 2) or between two of the aluminum oxide coated plates 11 (FIGURE 3), in which case, the insulating ring 19' may provide a shoul- 'der on which the resistor 18 sits or between the upper aluminum oxide coated plate 11 and the metal plate 16 (not shown in the drawings).

FIGURE 4 diagrammatically illustrates the incorporation of the shunt device of FIGURE 1 with a separate series connected resistor 18 in the lower part of a lamp case 25 of a miniature lamp 23. Such a shunt device with separate series connected resistor is indicated by reference numeral 10". The lamp 23 may have an Edison screw or bayonet or pin type socket 20 of which the contacts 22, 22 are diagrammatically illustrated. It will be seen that the shunt device 10" (consisting of simple shunt 10 and resistor 18) are connected in parallel across the terminal contacts 22, 22 of the lamp socket 20. The complete lamp unit designated 31 shown in FIGURE 4, would normally be employed as the first lamp unit of a light set as shown in FIGURE 5. The resistance of the resistor is preferably equal to or greater than the resistance of a series connected light set.

FIGURE illustrates, diagrammatically, a set of miniature electric lamps 23 in a series connected circuit. As will be seen, the lamp cases 21 each'have a shunt device or 10' incorporated therein. The shunt device 10 of the first unit 31 is preferably as described in relation to FIGURE 4. The shunt device of the second and sub sequent units 32 may be of the kind illustrated in FIG- URES 1, 2 or 3.

The second unit is illustrated as having a simple shunt 10 of the kind shown in FIGURE 1. With a shunt device It)" in the first unit subsequent units with shunt devices 10 are perfectly satisfactory. The third unit is illustrated as having a shunt device 18" in which case the resistor 18 incorporated therein acts as a current limiting means. If all the units: have a shunt device 10", a unit 31 is not necessary. The case 21 may be integral with the socket 211.

FIGURE 6 diagrammatically illustrates a further use of the invention as applied to conventional series connected sets of decorative lamps. The individual lamps may be of any type with shunt devices as hereinbefore described in relation to FIGURE 1 or of any existing known kind incorporated in the lamp bulbor in the lamp base.

A master control lamp 24 has a case 25 having a shunt and resistor device 26 similar to the shunt device 10". The resistor of this device has a value equal to or greater than the resistance of the whole set. The shunt of the device being constructed in accordance with FIGURE 1 and having a separate resistor 18. The device being located within the lamp case 25, as. shown. The lamp 24 has a current rating preferably slightly less than that of anordinary lamp of the set.

The master control lamp 24 may be, as shown, provided with a flexible connector 27 having a lamp base 28 for substitution for one of the bulbs of an existing set. Alternatively, the master control lamp 24 and a case 25 may be incorporated in a set of decorative lamps, for example, on the first bulb. In a further embodiment shown in FIGURE 7 the case 25 may be adapted to plug or screw into an empty socket of an existing set so that a flexible connector 27 is not needed.

In operation, should a lamp of the set fail, then, under normal conditions, the lower rated master control lamp Will fail next. Its shunt resistor device 26* then comes into operation and passes a reduced current which is just snfiicient for the working lamps to light dimly and for the non-Working lamps, the original lamp failure and thei1 master control lamp to be signalled by failure to lig t.

The master control lamp can be used in a further way, for testing a set of lamps. Normally, if several lamps have failed or are loose in their sockets their shunt devices come into operation and a high current flows, usually sufficiently high to damage several other lamps in the set. If the lamp 24 is loosened or removed from its socket, the remaining lamps of the set will glow dimly or, any lamps which may be loose in their sockets or may have failed will fail to light. Such lamps may be tightened in their sockets and the sockets tapped (to break the shunt) and, if they then glow dimly, do not need replacing. Those lamps which fail to glow, of course, need replacing.

The invention is capable of further simple modifications as illustrated in FIGURES 8 and 9 or FIGURES 10 and 11 hereof. FIGURES 8 and 9 illustrate a flasher bulb combined master control unit, FIGURE 8 being a circuit diagram and FIGURE 9 being a diagrammatic section of the unit. As shown, a flasher bulb 40 incorporating a bi-metal breaker 41 is connected in series with a master control unit comprising bulb 24 and a shunt resistor device 26. FIGURE 9 illustrates the relative mounting of the parts without the bulbs, a socket 42 being shown for the flasher 1521b 40 and a socket 29 being shown for the master bulb FIGURES 10 and 11 illustrate, respectively, a circuit diagram for, and a diagrammatic section of, a socket adaptor arranged to be interposed between a Wall socket (not shown) and the plug of a series connected set of decorative lamps. As shown in FIGURE 11, a Bakelite or like casing houses the bulb 24 and the combined series resistor and shunt device 26. The casing has, at one end, pins 44 for electrical engagement with, for example, a wall socket, and at its other end, socket holes 43 for receiving a plug (not shown) on the end of a. series connected set of decorative lamps.

Referring to FIGURE 10, there is diagrammatically illustrated a first pair of terminals 44 adapted to be connected to a mains supply, a second pair of terminals 43 adapted to be connected to a set of series connected decorative electric lamps, a lead 45 connecting a respective one of each pair of terminals 44, 43, a control lamp 24 connected in series between the other terminals of said pairs, and a shunt resistor device 26 connected in parallel with the lamp 24. The circuit diagram of FIGURE is also common to the adaptor of FIGURE 15.

FIGURE 11 shows an embodiment of an adaptor having master control unit in accordancewith the present invention. As shown, the first pair of terminals 44 are constituted by plug pins projecting from a moulded Bakelite or polycarbonate casing 46 and arranged for insertion into a conventional two pin socket outlet (not shown). One of the pins 44 is connected by the lead 45 to one of the second pair of terminals 43 constituted by socket outlets at the opposite end of the casing. The other pin 44 is connected to a base contact of a lamp socket, a wall contact of which is connected by a lead to the other terminal 51. A shunt device 26 is connected in parallel with the lamp socket. A replaceable control lamp 24 is insertable into the lamp socket.

The diagram of master control unit, illustrated in FIG- URE 12 is identical to that illustrated in FIGURE 10 except in that besides the terminals 43 (which provide sockets for reception of a two-pin plug) a further set of terminals 43a which provide direct connections for flex leads 47 (as shown in FIGURE 13) of a set of series connected decorative electric lamps are provided inside the casing. The flex leads 47 enter the casing 48 of the unit through an aperture 49 in the side wall thereof.

The connections and various parts within the casing 48 are represented separately in FIGURE 13. As shown, each of the terminals 44 is connected by a respective lead 45 to one of the socket terminals 43. One of the pins 44 is connected to a base contact of a lamp socket 20, a wall contact of which is connected by a lead 50 to the respective one of the further set of terminals 43a. A shunt device 10, connected in series with two series connected resistors 18 (and forming therewith a shunt resistor device 26), is connected in parallel with the lamp socket 20. A replaceable control lamp 24 is insertable into the socket 20.

FIGURE 14 illustrates a plurality of master control units shown in FIGURE 13 and indicates the manner in which they may be connected end-to-end to permit a corresponding number of sets of series-connected decorative electric lamps to be connected to one mains socket outlet. The number of units which can be so employed is limited only by the mechanical strength of the control unit and by the current carrying capacity of the socket outlet.

FIGURE illustrates a further embodiment of adaptor which differs from those shown in FIGURES 12 and 13 only in that the second pair of terminals 43' are located within the casing 51 and the flex leads 47 are connectable directly thereto, through an aperture 52 in the end of the casing. Such an adaptor would replace the normal plug on the end of a conventional set of series connected decorative electric lights.

Due to the increased size of master control unit permitted by the above embodiments, the problem of heat dissipation is minimized. Moreover, the master control unit is, by its location for connection to a mains electricity supply, normally located away from highly inflammable decorative materials.

The embodiments of FIGURES 13 and 15 are particularly advantageous in that the necessity for a conventional plug to be employed on a set of decorative lamps is avoided.

The invention therefore provides several advantageous features: firstly a shunt device of accurate, simple and relatively inexpensive construction; secondly current reducing means or current limiting means for use in conjunction with the shunt device so as to limit the current which normally flows through its respective or several of the shunt devices when the latter are in operation; thirdly a set of decorative lamps of construction such as to reduce the fire hazard normally associated with shunted series connected lamps; and fourthly to provide a master control lamp for use in conjunction with or for incorporation into a set of series connected decorative lamps having shunt devices so as to reduce the cost of such set whilst simultaneously maintaining the fire hazard at a minimum, such master control lamp also serving as a test unit for a set of lamps.

I claim:

I. A shunt device for connection in parallel with the filament of an electric lamp connected in a series circuit comprising; a metal casing having a bottom wall portion,

side wall portions and an inturned top edge portion defining an opening in the top of said casing; aluminum plate means having an aluminum oxide coating on opposite surfaces thereof; an uncoated metal plate; insulation means connected about the perimeter edges of said aluminum plate means and uncoated metal plate and connecting said plate and plate means in superimposed spaced relation within said metal casing insulated from said bottom wall portion, side wall portions and top edge portion thereof;

" said aluminum plate means connected in spaced relation adjacent said bottom wall portion and defining a first chamber therebetween; said uncoated metal plate connected adjacent said top edge portion and spaced from said aluminum plate means and defining a second chamber therebetween; electrically conductive granular material loosely packed in said first and second chambers so as to be easily movable upon vibration of said casing; said metal casing constituting one terminal and said uncoated metal plate constituting another terminal of said shunt device; electrical connections connecting said terminals in shunt with the filament of the electric lamp to form an alternative path for current flow when the resistive load of the filament is removed, and said inturned top edge portion maintaining said plate, plate means, granular material and insulation material in the respective positions in said metal casing.

2. A shunt device as set forth in claim 1 in which said metal casing is cylindrical, and said insulation means include stacked rings of insulation material, certain of said rings having a recessed groove about the inner bore thereof, and said aluminum plate means and uncoated metal plate connected in the recessed groove of a respective certain ring.

3. A shunt device as set forth in claim 1, including a disc of electrically resistive material connected between and in electrical contact with the granular material in said first chamber and said bottom wall portion, and the edge portion of said disc insulated from said side wall portions by said insulation means.

4. A shunt device as set forth in claim 1 in which said aluminum plate means comprise a pair of aluminum plates having aluminum oxide coatings on opposite surfaces, said pair of plates defining a third chamber therebetween, and said electrically conductive granular material loosely packed in said third chamber so as to be easily movable.

5. A shunt device as set forth in claim 1 in which said electrical connections include an electrical socket releasably engaging the electric lamp.

6. An adaptor for connecting the pair of electrical conductors of a set of series-conected electric lights to a pair of power terminals of a source of electrical power comprising, a casing of insulation material, a first pair of terminals connected to said casing for releasable connection with the pair of power terminals of the source of electrical power, said casing including a second pair of terminals connectable to the pair of electrical conductors of the set of series-connected electric lights, a first electrical connection between one terminal of each of said first and second pairs of terminals, a lamp in said casing connected across the other terminal of each of said first and'and second pairs of terminals, a shunt device in said casing comprising a metal housing having a bottom wall portion, side wall portions and an inturned top edge portion, aluminum plate means having an aluminum oxide coating on opposite surfaces, an uncoated metal plate, insulation means connected about the perimeter edges of said aluminum plate means and uncoated metal plate and connecting said plate and plate means in superimposed spaced relation within said metal housing insulated from said bottom wall portion, side Wall portions and top edge portion thereof, said aluminum plate means connected in spaced relation adjacent said bottom wall portion and defining a first chamber therebetween, said uncoated metal plate connected adjacent said top edge portion and spaced from said aluminum plate means and defining a second chamber therebetween, electrically conductive granular material loosely packed in said first and second chambers so as to be easily movable, and a pair of electrical connections respectively connecting said metal housing and uncoated metal plate across the said other terminal of each of said first and second pairs of terminals to form an alternative path for current flow when the resistive load of said lamp is removed.

7. An adaptor as set forth in claim 6 including a third pair of terminals connected to said casing for releasable connection with another set of electric lights, said first electrical connection also connected to one terminal of said third pair of terminals, and a second electrical connection between the other terminal of each of said first and third pairs of terminals.

8. An adaptor as set forth in claim 6 in which said first pair of terminals comprise a pair of plug pins protruding from said casing.

9. An adaptor as set forth in claim 6 in which said second pair of terminals comprise a pair of plug socket members for releasably engaging the respective pins of a plug member connected to the pair of electrical conductors of the set of series-connected electric lights.

10. An adaptor as set forth in claim 7 in which said third pair of terminals comprise a pair of plug socket members for releasably receiving the respective pins of a plug member on the said another set of electric lights.

References Cited UNITED STATES PATENTS 1,024,495 4/ 1912 Booth et al. 315-122 1,343,039 6/1920 Dantsizen- 200-118 1,681,491 8/1928 Eckhardt et a1. 315- 1,692,272 11/ 1928 Lampl 200-118 1,878,153 9/1932 Lampl 315-75 2,079,174 5/1937 Kamm 200-118 2,134,392 10/1938 Barwood 200-118 2,336,903 12/1943 Van Horn 315-75 FOREIGN PATENTS 154,863 11/1938 Austria.

BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner. 

1. A SHUNT DEVICE FOR CONNECTION IN PARALLEL WITH THE FILAMENT OF AN ELECTRIC LAMP CONNECTED IN A SERIES CIRCUIT COMPRISING: A METAL CASING HAVING A BOTTOM WALL PORTION, SIDE WALL PORTIONS AND AN INTURNED TOP EDGE PORTION DEFINING AN OPENING IN THE TOP OF SAID CASING; ALUMINUM PLATE MEANS HAVING AN ALUMINUM OXIDE COATING ON OPPOSITE SURFACES THEREOF; AN UNCOATED METAL PLATE; INSULATION MEANS CONNECTED ABOUT THE PERIMETER EDGES OF SAID ALUMINUM PLATE MEANS AND UNCOATED METAL PLATE AND CONNECTING SAID PLATE AND PLATE MEANS IN SUPERIMPOSED SPACED RELATION WITHIN SAID METAL CASING INSULATED FROM SAID BOTTOM WALL PORTION, SIDE WALL PORTIONS AND TOP EDGE PORTION THEROF; SAID ALUMINUM PLATE MEANS CONNECTED IN SPACED RELATION ADJACENT SAID BOTTOM WALL PORTION AND DEFINING A FIRST CHAMBER THEREBETWEEN; SAID UNCOATED METAL PLATE CONNECTED ADJACENT SAID TOP EDGE PORTION AND SPACED FROM SAID ALUMINUM PLATE MEANS AND DEFINING A SECOND CHAMBER THEREBETWEEN; ELECTRICALLY CONDUCTIVE GRANULAR MATERIAL LOOSELY PACKED IN SAID FIRST AND SECOND CHAMBERS SO AS TO BE EASILY MOVABLE UPON VIBRATION OF SAID CASING; SAID METAL CASING CONSTITUTING ONE TERMINAL AND SAID UNCOATED METAL PLATE CONSTITUTING ANOTHER TERMINAL OF SAID SHUNT DEVICE; ELECTRICAL CONNECTIONS CONNECTING SAID TERMINALS IN SHUNT THE FILAMENT OF THE ELECTRIC LAMP TO FORM AN ALTERNATIVE PATH FOR CURRENT FLOW WHEN THE RESISTIVE LOAD OF THE FILAMENT IS REMOVED, AND SAID INTURNED TOP EDGE PORTION MAINTAINING SAID PLATE, PLATE MEANS, GRANULAR MATERIAL AND INSULATION MATERIAL IN THE RESPECTIVE POSITIONS IN SAID METAL CASING. 